Deposition of immunoglobulin A1 (IgA1) in human tissues and organs is a characteristic of many human diseases including IgA nephropathy, dermatitis herpetiformis, and Henoch-Schoenlein purpura. IgA nephropathy (IgAN) is the most common form of glomerulonephritis throughout the world (Emancipator et al. 1998 and Emancipator et al. 2005). IgAN is characterized by presence of mesangial deposits containing complexes of IgA1. Clinical symptoms of IgAN include proteinuria, hematuria, and hypertension that may evolve into end-stage renal disease.
IgA1 proteases are bacterial enzymes that specifically cleave IgA1 molecules at their hinge regions (See FIG. 1). Recently, systemically administered IgA1 protease has been shown to remove glomerular IgA immune complexes in a mouse model of IgAN (Lamm et al. 2008). Thus, IgA1 protease is a promising therapeutic agent for treatment of IgA1 deposition diseases such as IgAN.